With this hot weather we are having in the Pacific Northwest (and my XJS in my shop addressing an oil leak that made a new if my engine bay I detailed last winter), I have a renewed interest in getting my seldom used XJ12 back on the road.
A few issues to sort out:
There is a shudder. I just took it to the tire shop and they balanced the wheels (free of charge, nice of them). I took it for a drive after getting it back. It started out fine. Drove a couple miles on the interstate, exited, drove a couple miles on surface streets, got back on the interstate, and when I hit the brakes the shudder started again. And itâs not just when the brakes are applied, but thatâs what starts it. I exited the freeway and continued getting a shudder whether or not the brakes were applied.
âTrac Failâ and âAnti Lockâ lights are on.
Upon parking the engine temp crept up and there was a noticable amount of coolant on the ground. It was coming for the bottom side of the header tank (atmospheric catchment tank).
My thinking is
Front brake job for number 1.
Cleaning the wheel sensors for number 2.
And for what Iâve read on here, starting with a new call on the header tank for number 3.
If anyone has any further ideas, please let me know.
I would check the front calipers. I spent alot of money trying to solve the same problem on my Rolls Royce Silver Shadow. When driving the car (like yours), it would be silky smooth UNTIL I pressed the brake pedal a few times. After that, it drove terribly. Simple to check! Stop the car and touch the hubcap (rim) and see if one is very hot. With mine, the caliper was not releasing because of the brake hose not letting the brake fluid return to the reservior.
Thank you, Richard. That was along my line of thought. I was thinking maybe the rotors werenât true and then the pads were being held a little too close (or progressively getting closer and closer with each press).
I replaced the cap on the header tank. First drive after that it still dumped coolant out after I parked. The second drive it didnât. Currently on the third drive testing the brakes and no coolant leaks yet.
If the overall coolant supply is overfilled, the excess will be expelled via a drain in the atmospheric catchment tank. The tank typically should be 1/2 full, after the coolant level stabilizes and is at ambient temps. Itâs a one gallon tank, so it allows for that volume of expansion as the system coolant heats up during a drive, and flows into the atmo tank. As the system cools, that coolant is then drawn back out of the atmo tank. SD Faircloth www.jaguarfuelinjectorservice.com
I let it barf out coolant until reached the point itâs happy, and then didnât add more. As long as it doesnât overheat, and the coolant level stabilizes, then the marked coolant level isnât important to me. If the level falls completely and the car runs warm thatâs another story.
I see your 1996 XJ12 may not have the atmospheric catchment tank, as does the XJS earlier models of the V12. It ( the XJ12) only has the expansion tank (aka recovery tank). In your first post at item #3, you refer to the item as the header tank, and in parenthesis ( atmospheric catchment tank). The header tank is under the hood. The atmospheric catchment tank is hidden in a cubby hole covered with a cover plate, at the rear of the front left wheel well. Threw me off. SD Faircloth
I donât have an XJ12, so I can only look at pics of a recovery tank. Nor can I find a decent hose routing diagram. If yours is leaking from the bottom, I fail to see how replacing the cap is going to resolve that. There is a hose that fits at the bottom of the tank, which I assume is the hose that routes (sucks) coolant back to the engine as it cools down. Possible source of your leak ? Also, yours may be cracked somewhere underneath ? Were it my vehicle, I would be removing the tank and hoses for a thorough inspection, albeit yours looks mighty clean. Also, donât understand two hoses entering from the side. ? SD Faircloth
ExceptâŚthe parts diagram for the XJ12 calls the item in Jayâs photo a expansion tank AND a recovery tank on the same page. Hence, more confusion for some.
The earlier model V12âs call it a header tank or an expansion tank, and the item at the rear of the left wheel wellâŚthe atmospheric catchment tank. SD
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